Management options for the unfavorable nutrient balance of recreational fishing in Lake Balaton (Hungary)

Various types of ground baits are loaded to lakes by anglers, but the ecological role of these materials is often overlooked. Thus, the aims of this study were to conduct a quantitative and qualitative assessment of the baits used by anglers in the largest lake of Central-Europe (Lake Balaton, Hungary), estimate the annual nutrient balance of recreational fishing, and relate the nutrient loading from this source to the total external load. Our study demonstrated that popular angler baits varied substantially in their nutrient contents and in their molar nitrogen to phosphorus (N:P) ratios. The net nutrient balance of recreational fishing was +19.3 t total N year(-1) and +5.2 t total P year(-1), equivalent to 0.7% and 3.2% of the estimated total annual N and P loads, respectively. The rate of nutrient loading may be doubled if the present trends continue: anglers will use 20% more bait with an even higher nutrient content and will also show higher propensity to release the fish after catching. In turn, sustainable nutrient balance of fisheries management could be achieved by limiting the anglers' bait use to 1.5 kg day(-1) and restricting baits to those which have relatively low P (<0.3%) and N (<1.5%) contents.